[clang][Driver] Don't warn when -nostdinc and -nostdinc++ are both specified (#77130)

When -nostdinc and -nostdinc++ are both specified and the Baremetal
toolchain is used, an unused command line argument warning for
-nostdinc++ is produced. This doesn't seem particularly meaningful as
-nostdinc++ would have been claimed/used had the check in
AddClangCXXStdlibIncludeArgs not short-circuited. So, just claim all
arguments in this check.

I believe this is consistent with what was done for the GNU toolchain
(see 6fe7de90), so hopefully this is
appropriate here as well.